The invention relates to fluidic connections, particularly to sealed for fluid connections to micro-machined devices, and more particularly to a zero dead volume tube-to-surface seal for fluidic connections, such as to micro-machined silicon wafers.
With the advent of micro-machined devices, making sealed fluidic connections to such devices has become an important technical issue in recent years because of the wide spread use of these types of devices.
The prior fluidic connections have primarily been made to the planar surface of the micro-machined devices, generally fabricated from silicon wafers. The common method for creating the ports on the surface of wafer devices is anisotropic etching. In this process the shape of the features etched are dictated by the direction of the slower etching planes of the silicon wafer and in [100] silicon (the most common wafer orientation) this creates either square or rectangular ports with angled walls. The most common shape for a fluid connection is tubular. This mismatch in shape makes a zero or low dead volume connection very difficult. Making this type of seal mechanically robust is also difficult. One solution to these problems is to create ports on the edges of the micro-machined devices. These ports can be made by isotropic etching which can yield near circular ports or by anisotropic etching which can approximate a circular port. In both cases the walls of these ports are perpendicular to the edge surface. There are advantages to making connections to the edge of the wafer devices. The first advantage is that the connection on the edge of a device takes up virtually no space on the wafer, and so the size of the device can be reduced compared to the planar surface connection. This reduction in size could be 50% or more. However, with the fluidic connections being made to the edges of the devices, there is a need for means of sealing these connections.
The present invention satisfies the sealing need by providing a zero dead volume tube to surface seal, which can be effectively utilized for gases and liquids. Basically the seal involves the use of a ferrule which forms both a seal about a tube and a seal on the ferrule/device mating surface. The sealing apparatus is simple in that it includes a body which retains a portion of a micro-machined device, and which has an opening having a thread section; a ferrule having an opening in which a tube extends; and a threaded fitting adapted to be inserted in the threaded opening for compressing the ferrule about the tube and against an edge surface of the micro-machined device, thereby forming a zero dead volume tube-to-surface seal.